This invention relates to a method for fully automatically feeding and transporting raw material of food products from bulk to a combination weigher, which then automatically selects from a number of portions of known weight the optimum combination required to make batches of fixed weight with minimum give-away.
The main purpose of the invention is to ensure that product is fed equally and accurately from bulk to the combination weigher, where the main feature of the invented method is, more precisely, the transporting of a measured and controlled amount of the food products from an infeed device to a combination weigher. The most important issue when feeding an combination weigher is to be able to control the average weight fed to the weighing hoppers which then weigh the product precisely. It is however not undesirable that there is some variation in the weight in each hopper as long as the average is kept at the desired level. The meaning of feeding the combination weigher precisely and accurately is therefore to be able to control accurately the average amount of product fed to the weighing hoppers.
Various types of infeed and dispersion equipment are known. These have been designed to feed a variety of products to automatic weighing equipment, including combination weighers. Most of this equipment is based on using vibration of some sort, and is designed for firm, non-sticky products, such as frozen food products, which do not tend either to stick together or to the surfaces of the equipment.
There are two main types of combination weighers; those in which the weighing hoppers are arranged circularly around a common axis, and others in which they are placed in a linear arrangement. In the former, the dispersion device is located at the centre of the circular array of weighing units, and the raw material is fed to its central portion dispersed in a radial direction and supplied to the pool hoppers. In the latter type, the dispersion device is located behind the weighing hoppers. Product is fed to the inlet end of the dispersion device and the outlet is next to the weighing hoppers. In both cases, however, the principle is basically the same, with an independent plate in front of each weighing hopper being vibrated when product is required in any given hopper. The main disadvantage of this method is that it is difficult to precisely control how much product goes into the hopper when the plates are vibrated.
Combination weighers do not always have one pool hopper above each weighing hopper. In some versions raw material in the pool hoppers can be weighed in such a way that better control is achieved of the weight of each product portion accumulated in the pool hopper before it is released to the weighing hopper. Other versions can include multiple pool hoppers placed above each of the weighing hoppers in order to ensure more rapid filling of the weighing hoppers. This is especially useful if the dispersion device does not feed product reliably when activated. Yet another variation is to place a pool hopper below the weighing hopper so that the product in the weighing hopper can either be released to the outlet trough or into the pool hopper. This gives the operator a greater variety of possible combinations as the weight of the product in the pool hoppers below the weighing hoppers is known. An increased number of possible combinations generally leads to better performance of the combination weigher in terms of reduced over-weight or increased capacity.
Several patents exist for dispersion devices. One of the first patents for an automatic weighing device with a dispersion device as a critical component is U.S. Pat. No. 4,398,612. Another, newer patent which also describes a dispersion device for dispersing product to a circular array of weighing hoppers is U.S. Pat. No. 4,561,510, and a similar device has also been patented in U.S. Pat. No. 4,600,096. These patents share in common the inclusion of multiple dispersion devices operating on the same pile of products. Each device can be individually controlled, and thus used to selectively feed multiple weighing hoppers or pool hoppers located above weighing hoppers.
Examples of combination weighers of the latter type mentioned above, that is those involving a linear arrangement of pool and weighing hoppers, are described in U.S. Pat. Nos. 4,442,910 and 4,821,820. However, these combination weighers do not provide automatic feeding into each hopper, and are therefore fed manually.
When processing sticky products—e.g. fresh fish, meat, fruit, vegetables or other similar fresh food products, dispersion devices which are based on the use of vibration as a means of transfer are no longer usable.
Several attempts have been made to design dispersion devices for sticky products that cannot be conveyed by vibration. One example is U.S. Pat. No. 4,662,508, where rotating discs in a horizontal plane are used to disperse the product. Another example is U.S. Pat. No. 6,493,605, where flexible tabs and vertical movement of the inlet chute are used to obtain more uniform feeding to the dispersion tables.
Neither of these two methods is sufficiently effective to convey sticky product reliably or accurately enough to the weighing hoppers. Furthermore, the quality of the handling of sensitive product such as fresh fish fillets or pieces is not acceptable.
It should, however, be mentioned that a combination weigher has been produced by Pols ehf, a company based in Iceland, which can be used to create batches of sticky food products, mainly fish, of fixed weight with minimum give-away. But as no automatic dispersion devices are connected to this weigher, it must be fed manually, which reduces its capacity. The need for manual labour to feed this combination weigher also makes it more expensive to operate.
For many years, very little progress has been made in the development of equipment for the packaging of fresh fish products. As a result, packaging remains a highly labour-intensive—and therefore expensive—activity in which give-away is higher than it need be if performed automatically using an accurate combination weigher. Further encouragement for the invention described comes from the fact that fish products are now being increasingly sold fresh from Iceland to markets in Europe, where the call is for smaller batch sizes. Whereas a few years ago these were often 10-15kg, a batch size of 2 kg is now common. As a result, the need for labour is even greater than before, with significant cash being lost due to unnecessarily high give-away.
It is therefore clear that none of the known methods or equipment is suitable for solving the problem of packaging sticky food product. The invention relates to a means of feeding sticky product, such as fresh fish products, quickly, precisely and accurately from bulk to a combination weigher, in such a way that the quantity fed will be well controlled.